I observe my naturally thin (and completely healthy) roommates and friends whose minds don't revolve around food. If I add up what they eat from morning to night, there's no way it even hits 900 calories. They seem healthy, energetic, and don't have sunken cheeks or protruding bones LOL. I feel like that's people's secret to staying thin, and they don't even realize they are doing it.

Can I get some thoughts on this? I'm not saying I'm right or wrong, I'm just saying what I've noticed. Thanks!!

I've seen far too many exceptions to that rule - and even a couple that go the other way, as in morbidly obese people who *maintain* on less than 1000 per day. Seems to me that if you're meeting your energy needs with what you're eating and you're not absolutely miserable ... try it and see what happens. One of our superstar maintainers used to say "We are all an experiment of 1". There are basic formulas that can get almost everybody headed down the right path, but experience says that there is nothing out there that will work for everybody, forever. Nothing seems to drive long-time maintainers crazier than needing to drop a few gained pounds, and discovering that the old formula doesn't work any more.

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I agree. Thats why I think that eating at maintenance creates taht woosh-its probably water weight. Sometimes I wonder if I should just "hold out" and just see if I get a (huge) woosh later by just sticking with the diet, or try eating at maintenance so I can see my "true" non water weight.
(edit-I mean there are extremities and exceptions to the rule, but I read somewhere that "fast" or "slow" metabolisms are rarer than we think-not saying its impossible, just less common than thought. I find that the very active thin people I know eat a lot, but they prob burn it off, and the less active thin people just feel like eating less and they might eat a lot when they eat out, but not when they get home etc etc, i know for me i just ate a ton all the time)

From leangains
The hypothesis has credibility if we look at the hormonal response to starvation diets. "Starvation diets" in this context simply mean any diet approach that results in a very high weekly caloric deficit created through diet and/or exercise. This is perceived as a significant stress to the body, to which it responds with chronically raised levels of cortisol. Some cortisol is great, but too much of it is very bad; and studies suggest that cortisol increases in a dose-dependent manner related to the calorie deficit. Prolonged elevations of cortisol can lead to massive water retention. If you've ever been treated with hydrocortisone, a pharmaceutical form of cortisol, you know what I mean.

* The above makes me wonder if the myth of "starvation mode" is actually perpetuated by extreme dieters who find themselves not losing any weight on starvation-level caloric intake (due to severe water retention obscuring weight loss). While some metabolic slowdown occurs during any diet, it's never so profound that it completely negates a substantial calorie deficit. For example, during The Minnesota Experiment the researchers noted a 15-20% reduction in basal metabolic rate at the end of the study (it was actually 40% compared to the start of the study, but this was due to a higher body weight; a large percentage of the drop could be explained by the simple fact that they weighed less and not due to any hormonal impact).

I have always, always advocated that if you have done the math, the calorie math, and you SWEAR you are only eating THAT MUCH and you are still not losing, firstly, stop lying about the three bites of brownie you snuck and didn't count, and secondly, start measuring your portions.

As far as your friends, and how much they eat, we really can't know for certain unless, of course, you start following them for a week at a time and measuring their food before they eat it. Which, I, um, cannot advise.

But I do advise that you get really strict about your food - measure your portions and don't sneak bites of anything -and get really strict about eating really clean, and I think you will see weight start to come off at higher calorie counts than you previously thought possible.

I've tired going under 1000 and for me it didnt work. I felt like I was starving. LOL

Some people can do it and some cant it just depends on your body and energy level.

Yah I think that in a way that low-cal hypothesis is dependent on the condition that you will maintain activity level no matter how you feel (so all the variables are constant other than cal level), which may or may not work for people in the real world, depending on how much you are willing to go through. Its all good-whatever works for anyone, but I just find it all fascinating lol.
You know what kind of boggles my mind sometimes? How even though I am eating at a cal deficit, I ate more nutrients than I ever did at 4000+ cal a day when i was a huge binger-because my diet was just comprised of 2 things-Nutella and lots and lots of cheap bread. Despite the huge quanitites, in a way, I was more "malnourished"(mal-nutritioned? whatever it is haha) than now lol.

I agree.I mean there are extremities and exceptions to the rule, but I read somewhere that "fast" or "slow" metabolisms are rarer than we think-not saying its impossible, just less common than thought. I find that the very active thin people I know eat a lot, but they prob burn it off, and the less active thin people just feel like eating less and they might eat a lot when they eat out, but not when they get home etc etc, i know for me i just ate a ton all the time

I was wondering the exact same thing. How does the OP know what these people are eating from sun up to sun down?

Sometimes my roommates and I will spend an entire Sat and Sunday together, for example. While I'll be constantly snacking and eating meals, they barely get up for lunch and something tiny for dinner and practically forget to eat snacks in between. I was serious when I said this happens right in front of my face lol!

A lot of 'naturally' thin folks end up calorie cycling in the long run. They eat a big meal and eat lighter the next day, or save their calories for spends like holidays or weekends, date night, etc, and maintain the rest of the time. And some very small people just don't take a lot of energy in, especially as they age they eat more lightly.

There are no rules, only general guidelines by which you start and adjust from there

A lot of people responding to this post are responding directly to your question about <1000kcal, but this is what stuck out most to me. In my Psych of Language class (of all places) we watched a video that touched on the way young children think about food. Some are naturally programmed to ignore food when they're not hungry (i.e., right after a meal) while others will eat a snack immediately after lunch if it's placed in front of them, even if it's during play time when they're focusing on other tasks.

Of course, plenty of other factors will be introduced in time–parents' eating habits and exercise are probably just the beginning–but I think there is a fundamental difference between the way people think about food, and it may not even be a dichotomy like the one mentioned in the video.

Whether your naturally thin friends are eating 900kcal or 1500 or 2200, it sounds like they aren't obsessed with food. Maybe they're the type who don't think about food if their body isn't actively asking for it and that allows them to avoid extraneous calories.